When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth

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Smoke from Canadian forest fires drifts over southwestern Greenland and the ice sheet. Modis satellite.

Kangerlussuaq, Greenland:

“SnowPiercer” is the big buzz action movie this summer – a Chris Evans Cli-Fi vehicle that follows a catastrophic rebellion on an apocalyptic bullet train in a dystopian snowy, ice-encrusted world – the result of geo-engineering gone terribly wrong. The climax is a CGI spectacular of cascading ice, twisting metal, charred bodies, and crashing train cars tumbling into vast chasms.

Probably wasn’t the best choice for viewing while strapped in to a metal tube 30,000 feet over the Greenland ice sheet. But if you’ve ever wondered what a collaboration between Terry Gilliam and Quentin Tarantino would look like, this is your meat. Think “Inglorious Bastards” crossed with “12 Monkeys.”

I mean that as a warning.

This will probably be my last post for a couple of weeks. OK, my second to last post.

I’m holed up for tonight at the Kangerlussuaq International Science Support center in the settlement of the same name, about 20 kilometers from the edge of the sheet. It’s where we staged many of our activities in last year’s Dark Snow mission, and well equipped for that – although not luxury accommodations by any means.

KISS, as its called by the scientists and graduate student who are the primary guests here, is a former Strategic Air Command barracks, and the nearby runway is, for that reason, one of the world’s longest – built to service B-52s.

Plenty long – but watch you don’t stray off course. Like Every airstrip I’ve seen in Greenland so far, there seems to be a zoning ordinance that there must be a sheer granite wall within a few meters of the runway. When the daily Airbus 330 “Mothership” from Copenhagen touches down, it’s customary for passengers to applaud.

Airstrip: check.500 foot rock wall: check.

The Arctic summer sun is blinding bright, and its a balmy 59 degrees F here, relatively close to the ocean. This valley is a bit of a meteorological anomaly and, outside of the Watson River, which flows from the edge of the ice and feeds into the world’s longest Fiord, the immediate vicinity is desert dry, with only scrubby vegetation running up the hillsides.

Looking south from the Airport

Watson River, looking east toward the ice sheet, about 20 km away.

Nearby, outside the rocky valley walls, it’s greener – but no trees. Trees are starting to crop up in southern Greenland, and there are some low bushes here, but nothing like a forest, or even a grove.

40 kilometers up on the ice sheet, where we’ll be hopping tomorrow early, its somewhere around freezing, and we expect, over the coming two week stay, that we will have a mix of sun, snow, and fog. How much of a mix will bear heavily on how much work we get done.

We’ll be in the epicenter of the part of the ice where melting has been accelerating most rapidly in recent decades, and the reason we are here is because no one yet knows precisely why.

In the spotlight this year is biologist Dr. Marek Stibal, who was up here in June to set up several experimental patches on the ice that will be enriched with nitrates to observe ice sheet organisms response to man-made nutrient inputs.

In addition to increased wildfires, the Dark Snow Team will be investigating the impact of algae and microbes, which, increasingly favored by warming temperatures, are gaining a larger foothold on the ice.

Dark Snow biologist Dr. Marek Stibal has found that a species of algae living on the ice produces a very special pigment that acts as a sunscreen, protecting it against the intense summer glare. The pigment is the very same molecule that gives black tea its color. The dark pigment, visible in many photos of ice during melt season, is an important, but not well understood, part of the darkening process.

As warmer temperatures spread over larger areas of the ice, more liquid water is made available – a vital factor for algae growth. In addition, scientists wonder whether industrial pollution may be delivering key nutrients like nitrogen and phosphorus to the ice, further driving algae growth.

The Association of Soybean and Corn Producers of the Mato Grosso region said farmers first noticed in March that their genetically modified (GMO) corn crops were less resistant to the destructive caterpillars that “Bt corn”—which has been genetically modified to produce a toxin that repels certain pests—is supposed to protect against. In turn, farmers have been forced to apply extra coats of insecticides, racking up additional environmental and financial costs.

The association, which goes by the name Aprosoja-MT, is calling on Monsanto, DuPont, Syngenta and Dow companies to offer solutions as well as compensate the farmers for their losses. In a release posted to the Aprosoja-MT website, spokesman Ricardo Tomcyzk said farmers spent the equivalent of $54 per hectare to spray extra pesticides, and that the biotech companies promised something they didn’t deliver, “i.e., deceptive advertising.” (via Google Translate)

But Monsanto et al. are unlikely to accommodate the farmers. According to Reuters, “seed companies say they warned Brazilian farmers to plant part of their corn fields with conventional seeds to prevent bugs from mutating and developing resistance to GMO seeds.”

Earlier this year, a similar problem arose in the U.S., when scientists confirmed that corn-destroying rootworms had evolved to be resistant to the GMO corn engineered to kill them.

The industry response to such loss of efficacy is not to encourage biodiversity, but to further modify the organisms, according to the nonprofit GM Watch.

The case of Brazil is an example for an overall trend showing that nearly twenty years after the start of commercialization of Bt crops, there are problems in several countries growing this kind of genetically engineered crop. Industry tries to tackle this issue by commercialization of so called “stacked events” that produce several different Bt toxins. The best known example is Monsanto’s SmartStax maize that produces six different Bt toxins.

Another unintended outcome is almost certainly an increased use of pesticides, as has already happened in Mato Grosso.

Scheduled for September 21, 2014, in New York City, the People’s Climate March will coincide with September’s UN Climate Summit, where world leaders including President Barack Obama and Chinese President Xi Jinping will be in attendance in answer to UN Secretary-General Ban Ki-moon summons to consult on climate change.

Key organizations, representing hundreds of thousands of New Yorkers and millions nationwide, hosted the press conference today to explain the goals of the mobilization and to share expectations for the UN summit. Representatives from New York City Environmental Justice Alliance, Sierra Club, 350.org, UPROSE and a number of local unions were there, as well as faith leaders, speakers from superstorm Sandy-impacted communities and millennials.

“The voice of youth is crucial in the People’s Climate March,” said Elizabeth Yeampierre, executive director of UPROSE. “They are the first and last generation that can make a difference in this global crisis. We have to work inter-generationally to build momentum for frontline communities and provide our people with the resources to address this complex issue.”

“With our future on the line and the whole world watching, we’ll take a stand to bend the course of history.” Photo credit: Clara Vondrich.

The People’s Climate March will highlight the climate crisis and the need to act now with bold solutions. More than 500 organizations—from community and labor groups to international NGOs and faith organizations—around the world have joined to organize or endorse the event. They describe the motivation for the march as follows:

With our future on the line and the whole world watching, we’ll take a stand to bend the course of history. We’ll take to the streets to demand the world we know is within our reach: a world with an economy that works for people and the planet; a world safe from the ravages of climate change; a world with good jobs, clean air and water, and healthy communities.

“To the untrained eye, this looks like an alliance of unusual bedfellows—labor joining hands with faith joining hands with national environmental groups,” said Eddie Bautista, executive director of New York City Environmental Justice Alliance. “But the idea that there is choice between environment and economy is a dated paradigm. The climate change march is not about slicing and dicing a political agenda—it’s a big tent. We invite all with an interest in the future.”

Bill McKibben, 350.org founder, hopes you’ll be there. In an EcoWatch blogpost he said, “We need to show just how big and unified our movement has grown, from the environmental justice advocates fighting fossil fuel pollution in our communities to the students demanding divestment on our campuses, from the scientists who have seen their warnings so far ignored to the clergy now showing real moral leadership.

If you’re wondering how to react to the devastating news that the Antarctic is melting out of control: New York. If you’re scared like I am by the pictures of the fire and drought across the West: New York. If you’re feeling like it’s time to change the trajectory of this planet: we’ll see you in New York.”

British Columbia's First Nations have fought the proposed Northern Gateway oil sands pipeline that would cross their land for years, and they have no intention of letting up just because the federal government recently approved it. They've ignored the wishes of Canadian Prime Minister Harper, shrugged off oil industry promises of local jobs, and rejected offers of part ownership in what could be a lucrative and long-lived project.

In short, they've been impervious to the kinds of political pressure and financial enticements that routinely succeed in smoothing the way for oil-related projects in the United States. How come?

A big part of the defiance comes from the Coastal First Nations, an alliance of aboriginal groups in British Columbia that has no interest in allowing diluted bitumen from Alberta's oil sands to pass through their territories or get shipped through their fishing grounds. The environment is too important to their culture, to their economy and to a succession of generations to come.

And because most First Nations in British Columbia never signed treaties ceding their lands or development rights to the Canadian government, they have been challenging projects in court—and winning. The latest and most significant court victory came in June, when the Canadian Supreme Court upheld aboriginal land titles and rights, and suggested that in places where land claims are not subject to treaties, First Nations may have de facto veto rights over projects on their territorial lands.

Art Sterrit (on right) on a fact-finding visit to Florida after BP's Gulf spill. "That was the biggest oil spill cleanup in history, and they couldn't clean it up. That was the death knell for the Northern Gateway for us."

Art Sterritt, executive director of the Coastal First Nations, has been a key player in the Northern Gateway saga. At 66, he's a goldsmith, sculptor and carver of totem poles and masks. But in serving on a tribal council, then becoming a treaty negotiator, and then joining the Coastal First Nations, Sterritt is following a family history of civic duty and activism. His dad, who turns 101 in early August, is a chief. He's also trying to make the world a better place for his 18 grandchildren.

In an interview with InsideClimate News, Sterritt elaborated on what's driving the First Nations' opposition to the Northern Gateway and why they can't be won over. The interview has been edited for brevity and clarity.

ICN: What is the Coastal First Nations and why was it formed?

Sterritt: We're an association of First Nations. We came together because of what the forest industry was doing. We were acknowledged by the provincial B.C. government as being the government in the region. Now we have ecosystem-based management practices so that you don't log at a rate that will wipe out the forest.

All of our communities have a land use plan. We have a marine use plan. What that means is that we're serious about our economy. We want to make sure that it's self-sufficient based on what's there, and that it doesn't harm the environment—so it lasts forever.

ICN: Why is protecting the environment so important for Coastal First Nations?

Sterritt: The area that we live in represents 25% of the coastal temperate rainforest left on the planet. So this is a very, very significant area. It's an amazingly beautiful area. Tourism is a huge, huge draw. So our communities are moving themselves toward renewable industries—industries that don't destroy the environment. We have carbon offsets that we get out of the forest. As we protect the forest, there's the ability to sequester carbon, which helps with the environment, and in return for that, there's revenue coming in.

ICN: How did Alberta's tar sands and the Northern Gateway project come into play?

Sterritt: We have invested, over the last 15 years, in excess of $400 million in this exercise [of planning for a sustainable economy]. We depend on the natural environment for the jobs that we have, and there's over 30,000 jobs on the coast of B.C. Right in the middle of all this arrives Northern Gateway, a project which actually jeopardizes everything. All those things we're doing, if you think about it, one oil spill, and all of those are over.

ICN: You don't think the pipeline and oil industry would protect your environment?

Sterritt: You're talking about an industry that doesn't have a culture of cleaning up their mess. Their culture is in covering up their mess with dispersants. We're still looking at what Enbridge did in the Kalamazoo River in Michigan. They haven't cleaned that up yet. They cleaned up 10-15% of the oil [from the Exxon Valdez] in Alaska. In the Gulf of Mexico, [BP] cleaned up something like six percent. They don't have the technology to clean up a spill in the ocean. It doesn't exist.

Click to enlarge

ICN: What about the promise of jobs and the prospect of an equity interest in the Northern Gateway project?

Sterritt: We're not a bunch of poverty stricken, illiterate people. This is a highly developed society—a culture that's sophisticated in terms of respecting the environment, recognizing what you need to do in order to maintain it, and with a sophisticated art form and languages and everything else. That's what they didn't realize. They just figured, oh we'll flash a couple jobs and a couple bucks under their nose, and they'll just jump up and down. When you have all that, and somebody comes along and offers you a few jobs, it's just a joke. You'll jeopardize more jobs than you're creating.

ICN: What does it mean to have the Supreme Court of Canada recently uphold aboriginal territorial rights?

Sterritt: It's been groundbreaking. What that means is that you can't just ride roughshod over First Nations. They do have rights. They do have title. And the title and rights are enshrined in the Constitution of Canada. Over the last 30 or 40 years, there have been over 200 court cases that First Nations have won where it lays out their right to fish, their right to hunt, their right to an economy, their right to their culture and their societies.

ICN: What is the Coastal First Nations' position on other kinds of economic development?

Sterritt: We're not against development. We are involved in industries that don't have the potential to wipe us out. For First Nations, the first thing they deal with is the environment. If they look at a project and see that the project is going to do irreparable harm to the place they've lived in for tens of thousands of years, it's not going to happen. If a project comes along that is not going to destroy what we already have, you've got a pretty good chance of the project moving ahead.

ICN: And you include liquefied natural gas (LNG) projects among those that could move ahead?

Sterritt: We are actively involved in helping develop a responsible natural gas industry. Those ships are big, and they would disrupt some of our harvesting and fishing and stuff, so we're working together to make sure that's done properly. Are you emitting too much carbon into the atmosphere? Are you contaminating the local airsheds where our people live? If there are impacts, they have to be mitigated. That's a pretty good formula for starting a conversation.

ICN: I heard that you went on a fact-finding trip to Louisiana and several other oil states along the Gulf of Mexico in 2011 after the BP Spill. What was the purpose?

Sterritt: We were in the middle of making a decision on whether or not we could support the Northern Gateway project. We had seen that the industry couldn't clean up Alaska, and we figured if anyone could [clean up an ocean oil spill], we would see it there. That was the biggest oil spill cleanup in history, and they couldn't clean it up. That was the death knell for the Northern Gateway for us.

ICN: You talk about an "oil culture" on the U.S. Gulf Coast and elsewhere. What does that mean?

Sterritt: That's the culture that the oil industry is trying to introduce us to. It's one that tries to create dependency from people that live in the region, and once they've created that dependency, they can do whatever they want.

If you look at those oil states, that's what they've done. Some people, even some First Nations people, seem to think that somehow we have to become part of this oil culture. It's not true. We don't need it. We have a really amazing culture. We don't depend on anybody but our environment. That's what it's about for First Nations.

Alberta is heading down that road, and they don't have a plan. A group like Coastal First Nations—well, we have a plan. Our plan doesn't include any industry that jeopardizes the plan.

Thanks to the courageous and indefatigable efforts of pipeline fighters everywhere, the tide has finally turned on Keystone XL. As it becomes increasingly clear that Keystone XL’s northern leg is not going through, it is time to set our sights on ending all tar sands exploitation.

The Obama administration’s latest election year delay on Keystone North is not a victory, but the dominoes continue to fall. Earlier this year, a citizen lawsuit denied TransCanada a route through Nebraska. Last month, it lost its permit through South Dakota. Now it faces a gauntlet of “Cowboys and Indians” vowing to stop it in its tracks.

We cannot let up until Keystone North is vanquished, but all signs point to President Obama nixing TransCanada’s cross-border permit after the November elections. Don’t just take my word for it.

On April 23, Rolling Stone contributing editor Jeff Goodell wrote: “I was told recently by members of the administration that the pipeline would, in fact, be rejected.” On June 18, former Vice President Al Gore wrote in this same magazine: “[Obama] has signaled that he is likely to reject the absurdly reckless Keystone XL-pipeline proposal.”

Both pronouncements come on the heels of former President Jimmy Carter pointedly warning the president that Keystone XL ”will define your legacy on one of the greatest challenges humanity has ever faced—climate change.”

For a president who has suddenly decided to stake so much of his legacy on addressing the climate crisis, approving Keystone North would destroy any shred of credibility on this issue. It would also put an administration that prides itself on outreach to Native American communities in the position of violating the 1868 Fort Laramie Treaty.

Tom Weis, David Lautenberger, Shane Red Hawk and members of his family and tiyospaye (Lakota for “extended family”) viewing the 1868 Treaty of Fort Laramie in the National Archives vault in Washington, DC.

I recently had the honor of viewing the Fort Laramie Treaty with Shane Red Hawk and his family in the National Archives vault. There wasn’t time to read every word of the hand-written document, but there was time to absorb the meaning of the “bad man” clause in Article I on the faded first page:

If bad men among the whites, or among other people subject to the authority of the United States, shall commit any wrong upon the person or property of the Indians, the United States will, upon proof made to the agent, and forwarded to the Commissioner of Indian Affairs at Washington city, proceed at once to cause the offender to be arrested and punished according to the laws of the United States.

Tribal leaders mounted on horseback in front of the Capitol Building en route to the “Reject and Protect” tipi encampment in Washington, DC.

Because Keystone North would cross treaty territory, its construction would blatantly violate the “bad man” clause, an arrestable offense the Great Sioux Nation will not abide. President Obama knows this because the presidents of the Oglala Sioux and Rosebud Sioux tribes declared on national television their people are “willing to die” to stop it. He also knows this because his senior counselor, John Podesta, visited the “Reject and Protect” tipi encampment on the National Mall in April where this declaration of nonviolent civil resistance was made.

As fate would have it, I found myself standing next to Mr. Podesta at this historic event. I thanked him for his public opposition to Keystone, then asked him to urge the president to use his bully pulpit to speak out against all tar sands exploitation (this includes preventing the tar sands barons from gaining a foothold in Utah’s pristine red rocks country).

We should not be doing business with a misanthropic industry that knowingly poisons First Nations communities in Canada, with immoral disregard for its climate impacts on humanity. Fortunately, the U.S. is in a strong position to help starve Alberta’s landlocked tar sands beast by stopping the flow of tar sands crossing our border.

Last month, retired Navy SEAL Team 6 Commander David Cooper provided powerful ammunition for doing just that with his warning to the State Department that the Keystone pipeline is highly vulnerable to attack: “We need a serious national conversation about what we do to head off an attack. Until then, I’d offer a saying we used on the SEAL teams: ‘If you cannot defend a position, you shouldn’t take it.’ ” His threat assessment described as “the most likely scenario” a spill of more than 1 million gallons of “highly toxic” Keystone tar sands oil.

Caution demands that beyond rejecting the Keystone permit, President Obama order national security assessments on all tar sands pipelines crossing our border, and an immediate shutdown of the built-to-spill southern leg of Keystone XL in Texas and Oklahoma.

We need to heed the indictment of the tar sands industry issued by Ponca Nation matriarch and grandmother Casey Camp-Horinek of Oklahoma: “We’re suffering from environmental genocide from this extractive industry.” The closing ceremony she led on the final day of the “Reject and Protect” tipi encampment was soul searing. Gathered near the White House, we looked on as she knelt in the grass to pour some sacred water. What poured were her tears. We watched in reverent silence as she cried, and cried. The tears she shed were for all who weep for what is happening to our precious Mother Earth.

No more grandmothers must be made to cry. No more First Nations people must be made to die. The tar sand industry’s brutal assault on the human family—and all our relations—must be arrested.

Mark Your Cosmic Calendar: 775/775

One wonders if anyone felt it. Did Charlemagne feel it as he led his forces across Pagan Saxon Westphalia, knocking down Irminsuls and making everyone pretend to be Christian or else? Did the people of Baghdad, just becoming the world’s largest city, notice anything aside from their own metro-bigness? Did the Abbasid Caliph Muhammad ibn Mansur al-Mahdi have the impression something cosmic was going on that year, other than his own ascendancy to power? Or was it mainly some of the nitrogen molecules in the upper atmosphere that were changed, not forever but for an average of 5,730 years, by the event?

The bent tree like object is said by some to be the, or a, Irminsul, the “pagan” sacred object, destroyed by Charlemagne, much as one might destroy a hypothesis, either with, or about, trees.

A long time ago, probably in our galaxy but kind of far away, a cosmic event happened that caused the Earth to be bathed in gamma rays in AD 774 or 775. No one seems to have noticed. There is a mention, in 774, of an apparition in the sky that could be related, but talk of apparitions in the sky were more common back then, before they had certified astronomers to check things out. There is chemical and physical evidence, though, of the gamma ray burst. The best evidence is the large scale conversion of stable nitrogen isotopes into unstable carbon-14 isotopes in the upper atmosphere. As you know, radioactive (meaning "unstable") carbon-14 is created continuously but at a somewhat variable rate in the upper atmosphere. Some of that carbon is incorporated, along with regular stable carbon, into living tissues. After the living tissue is created and further biological activity that might retrofit some of the carbon atoms ends (i.e., the thing dies) the ratio of radioactive carbon to stable carbon slowly changes as the radioactive carbon changes back into nitrogen. By measuring the ratio now, we can estimate how many years ago, plus or minus, the originally living thing lived and died.

But it does vary. Solar activity, nuclear testing, other things, can change the amount of carbon-14 that gets produced. And, a cosmic event that happened in 774/775 caused the production of enough carbon-14 to throw off the chronology by hundreds of years. This is seen in the close examination of carbon in the tissue of trees placed in a tree ring chronology. For example:

Original caption: High-resolution radiocarbon ages, superimposed on annually resolved radiocarbon measurements from Japan and Europe (grey lines and crosses) as well as the IntCal calibration curve based on decadal samples (blue shading), re-sampled at 5-year intervals (light blue crosses). Radiocarbon ages (that is, using 14C, 13C and 12C isotopes) were determined at ETHZ with the MICADAS system.

See the inverted spike there? That is, apparently, gamma rays messing up the radiocarbon chronology. Hold that thought.

Climate Change Is Hard

When volcanoes erupt, they typically spew crap into the air. Some of this material stays in the atmosphere for a while (called aerosols, but not your under-arm deodorant exactly), which will in turn reflect sunlight back out into space prematurely. This causes cooling. It is essential to know how much cooling of the atmosphere happens from aerosols because this is a potentially important factor in global warming. The effect of aerosols caused by volcanoes or industrial activity is an important term in the big giant equation that puts all the different factors together to produce global warming (or cooling). It is important that climate models be able to accurately and realistically incorporate the effects of aerosols. If the science isn’t right on aerosols, climate models may not run true when aerosols are included.

Caldera of Mount Tambora. When Tambora erupted in 1816, we experienced a year without a summer. Tambora was small compared to many earlier volcanoes which may have produced a few summer-less years in a row.

And indeed there is an apparent problem. When climate models are run and include aerosols, and the results are compared with real life data where we have good proxy-indicators of past climate, the model predictions and the real life measurements don’t line up when aerosols are involved at any significant level. A big volcano goes off, but the proxy record consisting mainly of things like tree rings doesn’t show the level of cooling models predict. This has titillated denialists, as you might imagine, because it shows how the science has it all wrong and the only way to truly understand the climate change is to spend hours in the basement with your spreadsheet and a good internet connection, like Galileo would have done.

In fact, this was an interesting problem that needed to be addressed. The modeling methods had to be wrong, or the paleodata had to be wrong, or something had to be wrong.

In 2012 Michael Mann, Jose Fuentes and Scott Rutherford published a paper in Nature Geoscience proposing a hypothesis to explain this discrepancy. The problem was that when a known volcano went off, the tree ring record in particular tended to show only an anemic result. Volcanoes that were thought to totally mess up the weather seemed to have little effect on trees. This even applied to volcanoes which were very directly observed in recent times, when we know there was an effect because people were putting on sweaters and measuring things with actual thermometers.

Mann et al. proposed that rather than having little effect on tree growth, the volcanoes had a huge effect on tree growth. What was being seen by the dendrochronologists (tree daters, like tree huggers but more serious) as a normal, average growth ring at the time of a volcanic eruption was actually the ring for the next year in line; they were missing, understandably, one or more growth rings. The volcano goes off, the trees don’t grow at all. (The masquerading ring would typically be the year before the missing ring since dendrochronology is done backwards, since we know what year it is now.)

You don’t have to imagine a year in which no tree grows ever anywhere to accept this idea. The trees being used as temperature proxies are more the sensitive type. They respond to temperature changes by growing more or less (warmer vs. cooler). Trees that don’t do this are not chosen for study. This has to do with the species and the setting the tree grows in, combining to make temperature the key limiting factor most years, so that growth ring width reflects temperature more than any other factor. So yeah, when it gets very cool because of a big-ass volcanic eruption, one of those “year with out a summer” deals, the very sensitive trees respond by not growing at all that year. They may have a growth period of a few weeks, but trees don’t simply lay down wood every day they are biologically active. They usually start with leaves, then many move on to reproduction, and once they have finished reproducing, have a cigarette, wash up, whatever, they may lay down wood or roots. (Different species have different patterns.) So, a very short growing season can mean no ring at all. If a really bad nuclear-winter-esque volcano happens, this may go on for a few years. This leads to the growth ring corresponding to the year of the volcano simply not being noticed by the dendrochronologists, with a different year standing in. Over time the record can be thrown off by several years, if there are a few volcanoes and one or more of them affects growth for more than one year.

So two things happen. Years with a very strong cold signal are lost entirely, and the record is quasi-randomly offset by a few years in some but not all tree records (because some will be thrown off, while others are not), so the collective record gets out of alignment. A strong uptick in the signal (the zero growth year) does not contribute to the paleoclimate squiggle of temperature at all, and the other possibly contributing years (after the worst is over) are moved around in relation to each other and average in with less cold years. It’s a mess.

Consider the following made up numbers representing temperature over time. The top table is the hypothetical raw data of tree ring growth in relation to temperature across a very strong cold anomaly as might be caused by a massive volcanic eruption. Depending on the tree, there is one or more years of zero growth. The lower table is the same set of numbers but with the earlier years (top) shifted down to cover the zeros, because that is what would happen if a dendrochronologist was looking at the rings from more recent (bottom) to oldest; there would just be this void and it would be filled with the next data in line.

Here are the same data graphed showing a clear anomaly in the top chart, but the very clear anomaly utterly disappears because of missing rings and shifting sequences in the lower chart. This is an existential problem for ancient climate events. I squiggle therefore I am.

Mann et al. proposed adjustments to the record of proxy-indicators of temperature that accounted for missing tree rings at the time of major volcanic events. They made a good case, but it was a bit complicated and relied on some fairly complicated modeling.

Since the publication of Mann et al. there has been quite a bit of back and forth between the climate modelers and the dendrochronologists. I’ve assembled a list of publications and blog posts below. I’ll only very briefly summarize here.

The dendrochronologists had a bit of an academic fit over the idea that they had missed rings. Understandably so. As an archaeologist, I’m partly trained in dendrochronology. There was actually a time when I considered making it my specialty, so I had read all the literature on the topic. I can tell you that missing rings was a serious concern, and taken seriously, and seriously addressed. Seriously, there’s no way modern dendrochronologists would totally miss an entire year’s growth rings. They had ways of dealing with missing rings.

The thing is, it is actually possible to miss rings. Here’s why. The assumption in dendrochronology is that rings can be missed (or for that matter, added) for reasons that allow for correction by cross-dating growth-ring sequences with other trees or even other samples in a single tree. A particular part of a tree can be missing a ring while another is not (especially vertically; the lower part of a tree grows last in many species), or some trees in an area may be missing a ring, but others have that growth ring. This assumption is probably almost always valid; missing rings can be adjusted for by cross-checking across samples. But, if all of the trees of a given species and sampling area have one or more missing rings because of a major volcanic event, that won’t work. But this is not something dendrochronologists are used to.

2 + 2 = 774/775

Eventually Mann and his colleagues put two and two together and realize that the dendrochronologists had a way to test the hypothesis that would not rely on fancy dancy climate-modeling techniques, and that would potentially allow a better calibration of the tree growth-ring record for certain time periods. It was that gamma-ray burst.

That moment in time is a clear marker. Any system involving 14C spanning this time interval should show the spike. Well, what about tree ring records that span both a major volcano and the 774/775 event? If Mann et al. are right, an uncorrected tree-ring record would show a lack of correspondence of any spike at 774/775. But, if missing rings are assumed for sensitive tree records at the time of the volcano, and the tree-ring sequence for those trees shifted, perhaps the records will line up. That would be a test of the hypothesis.

And this is the gist of a letter to Nature from Scott Rutherford and Michael Mann. Very simply put, Mann and his colleagues took this graph, from an earlier paper:

And changed it to this graphic which shows mainly (see caption) the tree ring sequences that span both the 1258 volcanic eruption, which was a big one, and the 774/775 event.

This is a gauntlet, being respectfully thrown down. Mann et al. erected a hypothesis that missing tree rings are virtually universal in large parts of the dendrochronological sample for some events, were not accounted for in the tree-ring chronology, and have thus messed up the tree rings as a proxy-indicator for temperature. Various attempts to knock it down have not worked out. Now, Mann has himself provided an excellent way to assail his own idea. It is now up to the tree ring experts to try to knock this hypothesis down. I suspect Charlemagne might have had an easier time knocking down the Irminsul.

I asked Michael Mann how he felt about this latest development in the ongoing saga of the missing (probably) growth rings. He said, “I’m very pleased that we’ve reached some level of reconciliation with our dendroclimatology colleagues: there’s an objective test that is available to determine if there are indeed missing rings in some of the regional chronologies, as we have speculated to be the case. I look forward to seeing the results of those tests. We proposed a hypothesis, other scientists were skeptical of the hypothesis, and now there is a way forward for testing the hypothesis. In the end, a fair amount of good science will have been done, and we will have learned something. This is the way science is supposed to work.”